This invention relates to an improved process for converting coal or similar solid carbonaceous materials. More particularly, this invention relates to an improved process for liquefying coal and similar carbonaceous substances.
As is well known, coal may be converted to liquid and gaseous fuels which may, in part at least, be substituted for naturally occurring liquid and gaseous fuels. Moreover, these liquid and gaseous products may be used directly or converted to produce chemical feedstocks.
Of these several coal conversion processes proposed heretofore, the liquefaction processes yield a broader range of product distribution and, therefore, likely candidates for the production of alternates for petroleum derived fuels and chemical raw materials.
Of these several liquefaction processes heretofore proposed, those processes wherein coal is liquefied in the presence of a solvent or diluent, particularly a hydrogen donor solvent or diluent, and a hydrogen containing gas appear to offer the greater advantages. In these processes, liquefaction is accomplished at elevated temperatures and pressures and as previously indicated a broad range of gaseous and liquid products are obtained. For the most part, however, these processes result in high relative yields of higher boiling point liquids; i.e., products boiling in the fuel oil and vacuum gas oil ranges and relatively high yields of gaseous products. The bulk of the products obtained from these processes, then, are at best substitutes for coal and applications where coal could be used directly. Moreover, these liquids are highly aromatic containing, typically, in excess of 80% aromatics making the liquids unsuitable for use directly as jet fuel, diesel fuel or as an ASTM No. 2 fuel oil. The need, therefore, for a liquefaction process wherein liquid products useful as jet fuels, diesel fuels and/or as an ASTM No. 2 fuel oil are produced directly is believed to be readily apparent.